The Louisville Zoo is open for business as usual Tuesday while inspectors try to figure out why a miniature train derailed and sent 22 people, including 17 children, to hospitals.

One child was critically injured when three open-air cars and the engine fell off the rails Monday.

Kosair Children's Hospital did not immediately have an updated condition for the wounded child Tuesday morning.

The train circles the zoo along a two-mile track. Zoo spokeswoman Kara Bussabarger said the attraction has been around for about 40 years but the train that derailed was bought in 2000.

Officials said there were about 30 people on board when the cars went off their track behind a gorilla exhibit.

One person was trapped briefly but then freed, according to Bussabarger. In addition to the child in critical condition, another youngster was listed in serious condition, according to a hospital spokesman. The youngest among the injured was 2 months old, he said.

The ride will be closed until further notice.

Inspectors from the Kentucky Department of Agriculture are investigating.